1. Field of the Invention
The present invention relates to a bearing sealing device, and more particularly to a sealing device for bearing assembly that is designed for massive continuous production without requiring any subsequent treatment and provides an improved firmness to the bearing when it is mounted on the bearing assembly.
2. Description of the Prior Art
A conventional bearing sealing device that is mounted on a bearing assembly having an outer ring and an inner ring rotating relative to each other includes a backing ring and a sealing material molded to have a sealing lip. Typically, the bearing sealing device is obtained by vulcanizing any elastic sealing material and molding it together with the backing ring to the appropriate shape. Then, the bearing sealing device is mounted on the bearing assembly by inserting a fixing part of the bearing sealing device into a fitting groove in the bearing assembly by sliding. In most cases, to permit an easy insertion and mounting, the fixing part is usually molded in soft form without the backing ring.
When such bearing devices are molded, however, the molding process involves the steps of placing a backing ring in a metal mold correctly, adding a sealing material to the metal mold, molding them together into a shape, and removing the molded shape from the metal mold. Those steps are usually complicated. When the sealing material is molded, burrs are always produced from any excess material. Thus, the molded shape always contains such burrs when it is removed from the metal mold. Such burrs then must be removed. This additional step or subsequent treatment is also tedious.
One proposed solution addresses the above problem. In this solution, a punch is used to obtain a bearing sealing device. This method and the bearing seal obtained by this method are described in Japanese unexamined patent publication No. 54-68882. Briefly, the method is described below and illustrated in FIGS. 7 and 8. A backing plate a forming a backing ring 2' is combined with a sealing material b forming a sealing ring 3'. Then, the backing plate a and sealing material b are placed in a metal mold 11 where they are firmly held together, and are punched to a bearing seal shape by using a punch 4. This punching is performed by moving the punch 4 across the backing plate a and sealing material b from the side of the sealing material b toward the backing plate a, as shown by an arrow 12 in FIG. 8. As the punch 4 is moving downwardly as shown by the arrow 12, it presses the upper side portion of the sealing material b and causes it to move peripherally as shown by an arrow 13, and the punching is then performed with the upper side portion of the sealing material h extended toward its periphery. The upper side portion of the backing plate a and the lower side portion of the sealing material b engage each other so closely that they cannot be moved relative to each other. When the punching is completed, the sealing material b includes a sealing lip 10 (as shown in FIG. 7) which is formed by the upper peripheral side portion of the sealing material b and extends beyond the punched peripheral edge of backing ring 2'. As shown in the above publication No. 54-68882, the bearing sealing device B obtained in the above method includes the backing ring 2' and sealing ring 3' formed by punching the resepective backing plate and sealing material together.
To permit an easy insertion and mounting, the bearing sealing device B is, in most cases, mounted to bearing assembly 1 by inserting it with the backing ring 2' facing inside and the sealing ring 3' facing outside, as shown in FIG. 7. When it is inserted in this way, the sealing ring 3' tends to be pulled by the backing ring 2' which prevents the sealing ring 3' from being seated in a fitting groove 6. In some cases, either of the backing ring 2' and sealing ring 3' may be detached wholly or partially from the other, or may be reversed. Thus, the sealing ring 3' cannot be seated firmly. The bearing sealing device B may easily slip out of the fitting groove 6 if vibrations or sways should occur on the bearing assembly. As the bearing sealing device B is not firmly secured to the bearing assembly, there is the risk that the bearing sealing device B may rotate with inner race or ring 1' in the bearing assembly.